/******************************************************************************
* FILE: bug1fix.c
* DESCRIPTION:
*   Solution for the bug1.c program.  The inc_count routine uses a
*   pthread_cond_broadcast() routine instead of the pthread_cond_signal()
*   routine.
* SOURCE: Adapted from example code in "Pthreads Programming", B. Nichols
*   et al. O'Reilly and Associates.
* LAST REVISED: 01/29/09  Blaise Barney
******************************************************************************/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define NUM_THREADS  6
#define TCOUNT 10
#define COUNT_LIMIT 12

int count = 0;
pthread_mutex_t count_mutex;
pthread_cond_t count_threshold_cv;

void *inc_count(void *idp) {
   int j,i;
   double result=0.0;
   long my_id = (long)idp;
   for (i=0 ; i < TCOUNT ; i++) {
      pthread_mutex_lock(&count_mutex);
      count++;

      /* 
	 Check the value of count and signal waiting thread when condition is
	 reached.  Note that this occurs while mutex is locked. 
      */
      if (count == COUNT_LIMIT) {
	 pthread_cond_broadcast(&count_threshold_cv);
	 printf("inc_count(): thread %ld, count = %d  Threshold reached.\n", 
		my_id, count);
      }
      printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", 
	     my_id, count);
      pthread_mutex_unlock(&count_mutex);
      
      /* Do some work so threads can alternate on mutex lock */
      sleep(1);
   }
   pthread_exit(NULL);
}

void *watch_count(void *idp) {
   long my_id = (long)idp;
   
   printf("Starting watch_count(): thread %ld\n", my_id);

   /*
     Lock mutex and wait for signal.  Note that the pthread_cond_wait routine
     will automatically and atomically unlock mutex while it waits. 
     Also, note that if COUNT_LIMIT is reached before this routine is run by
     the waiting thread, the loop will be skipped to prevent pthread_cond_wait
     from never returning.
   */
   pthread_mutex_lock(&count_mutex);
   printf("***Before cond_wait: thread %ld\n", my_id);
   pthread_cond_wait(&count_threshold_cv, &count_mutex);
   printf("***Thread %ld Condition signal received.\n", my_id);
   pthread_mutex_unlock(&count_mutex);
   pthread_exit(NULL);
}

int main(int argc, char *argv[]) {
   int i, rc;
   pthread_t threads[6];
   pthread_attr_t attr;

   /* Initialize mutex and condition variable objects */
   pthread_mutex_init(&count_mutex, NULL);
   pthread_cond_init (&count_threshold_cv, NULL);

   /*
     For portability, explicitly create threads in a joinable state 
   */
   pthread_attr_init(&attr);
   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
   pthread_create(&threads[2], &attr, watch_count, (void *)2);
   pthread_create(&threads[3], &attr, watch_count, (void *)3);
   pthread_create(&threads[4], &attr, watch_count, (void *)4);
   pthread_create(&threads[5], &attr, watch_count, (void *)5);
   pthread_create(&threads[0], &attr, inc_count, (void *)0);
   pthread_create(&threads[1], &attr, inc_count, (void *)1);
   
   /* Wait for all threads to complete */
   for (i = 0; i < NUM_THREADS; i++) pthread_join(threads[i], NULL);
   
   printf ("Main(): Waited on %d  threads. Done.\n", NUM_THREADS);

   /* Clean up and exit */
   pthread_attr_destroy(&attr);
   pthread_mutex_destroy(&count_mutex);
   pthread_cond_destroy(&count_threshold_cv);
   pthread_exit (NULL);
}

/* Output
Starting watch_count(): thread 4
Starting watch_count(): thread 2
Starting watch_count(): thread 3
Starting watch_count(): thread 5
inc_count(): thread 0, count = 1, unlocking mutex
inc_count(): thread 1, count = 2, unlocking mutex
***Before cond_wait: thread 4
***Before cond_wait: thread 2
***Before cond_wait: thread 3
***Before cond_wait: thread 5
inc_count(): thread 0, count = 3, unlocking mutex
inc_count(): thread 1, count = 4, unlocking mutex
inc_count(): thread 0, count = 5, unlocking mutex
inc_count(): thread 1, count = 6, unlocking mutex
inc_count(): thread 0, count = 7, unlocking mutex
inc_count(): thread 1, count = 8, unlocking mutex
inc_count(): thread 0, count = 9, unlocking mutex
inc_count(): thread 1, count = 10, unlocking mutex
inc_count(): thread 0, count = 11, unlocking mutex
inc_count(): thread 1, count = 12  Threshold reached.
inc_count(): thread 1, count = 12, unlocking mutex
***Thread 2 Condition signal received.
***Thread 3 Condition signal received.
***Thread 5 Condition signal received.
***Thread 4 Condition signal received.
inc_count(): thread 0, count = 13, unlocking mutex
inc_count(): thread 1, count = 14, unlocking mutex
inc_count(): thread 1, count = 15, unlocking mutex
inc_count(): thread 0, count = 16, unlocking mutex
inc_count(): thread 1, count = 17, unlocking mutex
inc_count(): thread 0, count = 18, unlocking mutex
inc_count(): thread 1, count = 19, unlocking mutex
inc_count(): thread 0, count = 20, unlocking mutex
Main(): Waited on 6  threads. Done.
*/
